The invention relates to electrical power steering system, and more particularly to methods and systems for payload estimation using electric power steering signals for consistent steering feel.
Traditional power-assist steering systems, such as Electric Power Steering (EPS) systems, are used in different vehicle classes ranging from light vehicles (small hatchbacks) to heavy vehicles (Pickup trucks, Vans). The electric motor acts as an actuator to assist the vehicle operator while steering the vehicle. Typically, EPS parameters are tuned to give optimal steering feel on various road surfaces for nominal vehicle load conditions. During use of the vehicle, payload may be added or subtracted from the vehicle. This change in payload changes the load, or force, exerted by each tire upon the road, which may significantly change a kingpin torque (and hence change rack load) when compared to the nominal load conditions. Changes in kingpin torque may result in an inconsistent steering effort ‘feel’ experienced by the operator. That is, the amount of steering effort may change with changes in payload for more traditional EPS systems.
Accordingly, it is desirable to develop an EPS system that is more robust, low cost, and/or may be capable of reducing inconsistencies in steering effort with changes in payload.